Disabled persons of all ages with marked neuromuscular weakness, paralysis, spasticity, bone and other physical deformities, or a combination of these or other maladies and conditions, often are confined to the seated, supine or prone position throughout their daily activities and in many cases are unable to sit or lie down properly. They often lack adequate trunk support and therefore may require a support or seating appliance to counteract tendencies for deformation or further deformation and which will permit them to function and to achieve some degree of comfort.
For example, in the case of wheelchair users, the selection of a suitable appliance in the form of a cushion between the person and the chair is an important factor in determining the degree of the person's independence and mobility since it has a significant impact on the length of time that the user can sit without developing problems such as painful discomfort or even decubitus ulcers (pressure sores). This in turn directly affects the type and extent of the activities, including education and employment, in which the user can partake.
Prior efforts at providing support and seating appliances have often proved inadequate because even with custom-contoured adaptive parts, they failed to meet the particular needs of the individual within reasonable cost. Furthermore, such prior systems have lacked one or more other requirements, including ease of fabrication, low weight (i.e., high strength-to-weight and mass ratio), resistance to soiling, ease of cleaning, non-flammability, temperature stability, and facile utility in the field.
A particularly important consideration in providing adaptive support systems for the physically disabled is the need to maximize the body surface area in contact with the cushion. It is generally agreed that pressure is a cause, not only of induced or aggravated physical deformity, but also of decubitus ulcers. Although the mechanism of decubiti formation is not completely understood, it is believed that pressure contributes to tissue destruction in three ways. First, pressure occludes blood vessels that supply oxygen and nutrients to the skin. Prolonged occlusion can cause ischemia and eventual necrosis. As pressure increases, the time required for tissue destruction is reduced. Second, pressure can cause mechanical destruction of the skin, and tissue that has been damaged by ischemia is more susceptible to such mechanical disruption. The third type of pressure damage, known as "autolysis", occurs when pressure is intermittently applied to tissue, whereupon an inflammatory reaction develops; the repeated application of such pressure causes the cells to release enzymes which catalyze tissue destruction.
Therefore, the incidence of decubiti can be decreased by reducing pressures encountered during sitting. The average pressure (P) is defined as the total force (F) over the total area (A), i.e., P=F/A. Since the total force, the body weight being supported, is essentially a constant, a reduction in average pressure is achieved by increasing the area supporting this weight. Furthermore, pressure should be distributed equally over the entire sitting area by equalizing the pressure at all points; this would have the added benefit of minimizing the occurrence of tissue-destructive shear forces parallel to the skin surface.
The foregoing considerations apply also to the more general problem of providing custom-seating for objects or masses which permit the object being supported to be kept in a given stable position for extended periods of time with minimum strain, e.g., splints and orthopedic casts for broken bones, seat cushions for vehicle operators, e.g., truck drivers, and packing molds for transporting delicate objects and equipment.
A need has therefore existed for an adaptive support system which is lightweight and relatively inexpensive to produce on a bespoke basis. In addition to the foregoing objectives, such a system should be capable of being readily formed from kits by technicians, physical therapists and other non-engineering personnel, and once formed should retain its shape with sufficient permanence so as to be re-usable by the subject without the need for re-molding.
Accordingly, it is an object of the present invention to provide an improved mass support system which is custom-contoured to the shape of the mass or object to be supported.
Another object is to provide an improved adaptive support system, such as a support appliance for the physically handicapped or disabled, which can be custom-contoured into a shape which is fixed in relation to the shape of the mass or object to be supported, whereby the weight of the latter is uniformly distributed over its interface with the support system.
Another object is to provide a method of producing an improved mass support system which is custom-contoured to the mass or object to be supported.
Yet another object is to provide a method of forming an improved adaptive support system, such as a support appliance for the physically handicapped or disabled, in which the system is custom-contoured into a shape which is fixed in relation to the shape of the mass or object to be supported, whereby the weight of the latter can be uniformly distributed over its interface with the support system.
These and other objects of the invention as well as a fuller understanding of the advantages thereof can be had by reference to the following disclosure and claims.